1. Field of the Invention
This invention generally relates to a drawbar arrangement for, and a method of, adjustably interconnectably positioning two wheeled cargo units of a vehicle at any one of a plurality of spacings apart from each other, as well as a remotely controlled suspension system for, and a method of, adjustably positioning a wheeled subframe at any one of a plurality of positions relative to a cargo unit of a vehicle.
2. Description of Related Art
A conventional truck, including a power unit and a van body for holding cargo, is typically pivotably connected by a kingpin assembly at a fixed pivot point to a semi-trailer which holds additional cargo. As considered along the direction of advancement of the vehicle, the van body is sometimes referred to herein as the front or leading cargo unit, while the semi-trailer is sometimes referred to as the rear or trailing cargo unit. The total cargo or payload of these cargo units depends on many factors, including the power unit rating, the type of material used in the construction of the cargo units, and the physical dimensions of each cargo unit.
It is conventional to interconnect the leading and trailing cargo units at a spacing along the longitudinal direction of advancement at a fixed distance on the order of 24 inches. This fixed spacing has been found to be quite satisfactory for highway travel. However, in some applications, for example, for city travel where the street grade is not altogether level, experience has shown that the top of the trailing cargo unit could hit and cause structural damage to the back of the leading cargo unit, particularly to the locking hardware on the top of the rear doors of the leading cargo unit. To prevent such damage, it would be desirable to space the cargo units apart at distances greater than 24 inches.
The fixed 24-inch spacing between the cargo units requires rollover dock plates to be placed on the floor to span the spacing between the leading and trailing cargo units when unloading or loading the same. Also, weather-protective shields must be installed overhead to span the distance between the cargo units. Such additional dock plates and shields must be separately carried on board and, aside from their tendency to be misplaced and lost, reduce the overall payload of the vehicle.
Still another problem associated with a vehicle having a fixed 24-inch spacing between the cargo units is that side doors are required to unload and load the vehicle. A 24-inch spacing is simply not enough for trucking personnel and cargo to fit through with clearance. In any event, many docking areas are designed to load and unload trucks through rear doors and, hence, the use of side doors for this purpose is not altogether desirable.
In order to provide a variable length connection between a pulled trailer and a tandem-connected trailer, the prior art has proposed, for example, in U.S. Pat. No. 4,230,335, a telescoping wheeled dolly. The dolly includes a number of tubes which are telescoped into and out of one another to the desired overall length to adjust the spacing between the trailers. However, such wheeled dollies are not load-bearing arrangements. The weight of the cargo in both trailers is supported entirely by the wheels and is not transferred through the telescoped tubes. Also, there is a considerable amount of lateral sway in such wheeled dolly designs due to the build-up of tolerances caused by the many interfitted tubes.
Related to the selective changing of the overall distance between the cargo units is the selective variation of the weight distribution of the payload relative to the wheels of the vehicle. U.S. Pat. No. 3,834,736 discloses an adjustable kingpin assembly operative for adjustably interconnecting a power unit of a truck and a trailer for varying the load distribution and overall length of the vehicle. Also known in the art are U.S. Pat. Nos. 4,738,462; 3,900,213 and 3,476,405.